Pyrazomycin is a nucleoside of structure ##SPC1##
First isolated from a fermentation broth of a strain of Streptomyces candidus characterized in U.S. Pat. No. 3,674,774 as "hitherto unknown". Like the triazole nucleoside 1-.beta.-D-ribofuranosyl-1,2,4-triazole-3-carboxamide [J. T. Witkowski, et al, J. Med. Chem. 15, 1150 (1972) R. W. Sidwell et al, Science, 177, 705 (1972)] pyrazomycin exhibits a substantial range of antiviral activity, which in at least the latter case is apparently related to competition with uridine metabolism. Unlike the former compound, however, pyrazomycin is a C-nucleoside, and a degree of toxicity associated with its employment in vivo (e.g., D. C. Delong, et al, Abstracta, VIIth International Congress of Chemotherapy, Prague, August 1971, A-5/35) may arise from resistance to detoxification occasioned by the stability of the C-glycosidic linkage. Like other C-nucleosides, pyrazomycin resists facile synthesis, although H. Farkas and others, in Tetrahedron Letters, 2279 (1972) have recently reported its obtainment by a protracted procedure commencing with ozonolytical cleavage of another C-glycoside. To our knowledge, no less inconvenient synthetic preparation of pyrazomycin appears in the literature.